1. Field of the Invention
This invention relates generally to fuel fill protective devices for fuel tanks, fuel fill lines and fuel vent lines, and more particularly to a marine fuel tank ullage valve. A novel ullage float valve assembly is disclosed which is secured to the fuel fill line at the point of entry into the top section of a marine fuel tank. Fuel tanks are subjected to diurnal temperature and pressure changes causing fuel to expand within the fuel tank, which in turn causes the deleterious effects of fuel expanding into the fuel tank ventilation line, or alternatively causing fuel to back up into the fuel fill line, and in either case fuel can be expelled from the system into the environment. The instant float valve assembly eliminates the need for accessory valves or protective canisters to be incorporated within the fuel vent lines, by providing a shut off mechanism during the fueling process, which simultaneously creates a ullage in the fuel tank thus preventing any liquid fuel from being forced into the ventilation lines during expansion.
2. Description of Related Art
Conventional marine fuel tank systems include the tank itself, the fuel fill line with a pressurized sealing fuel cap, and one or more fuel ventilation lines. The ventilation lines prevent pressure in the tank from exceeding regulations set by the federal government, as well as marine industry standards established by the American Boating and Yacht Council (ABYC). As the temperature rises, combustible fuel expands which creates a potentially dangerous rise in pressure within the fuel tank. The ventilation lines allow for fuel vapor to escape during the refueling process, thus preventing the fuel system from becoming over pressurized during fueling operations or because of thermal expansion. However, as fuel pumps, hoses and nozzles pump fuel at high volume per time increment, the fuel tank can reach capacity and yet the fueling operation continues which causes fuel to be pumped into the ventilation lines and/or back flow into the fuel fill line, both of which can be expelled into the vessel, the surrounding pump area, or the environment including the surrounding water.
Various attempts have been made to eliminate or mitigate the phenomenon of over filling fuel tanks, causing fuel to flow into the ventilation lines, creating back flow into the fuel fill line, and expelling gasoline into the environment.
U.S. Pat. No. 5,348,177 issued to Sung is entitled FUEL BACKWARD FLOW-PREVENTING DEVICE FOR USE IN AN AUTOMOTIVE VEHICLE, and discloses a custom designed fuel filler, fuel tank and a guide member which is connected to the inside nozzle of the main fuel fill line. The guide member includes a plurality of slits, and an inverted cone with legs members which travel through the slits. This device uses an air pocket within the inverted cone, and when the float member reaches the fuel fill line back pressure is created which shuts off the nozzle.
U.S. Pat. No. 6,138,852 issued to Miura et al. is entitled FUEL TANK, and discloses a check valve system which has a plurality of spray outlets on the head of the check valve. The check valve includes a housing having the plurality of openings, a valve member and spring biasing system to control movement. This system enters the side of the fuel tank, and is designed to cool down the fuel that is being stored within the tank body, thereby reducing the development of fuel vapor.
U.S. Pat. No. 6,837,256 issued to Benjey is entitled FILLER TUBE MOUNTED FUEL TANK REFUELING VALVE, and discloses a spring loaded poppet and spool valve assembly. A float operated latch is linked to the main valve body, and when the latch is released the spool valve is closed.
The prior art also contains additional designs incorporating a variety of nozzle receptors, breather-vent lines, conventional valves, spring valves and fuel filter/canister assemblies for fuel tanks and automobile systems, however none of this art addresses the specific solutions achieved by Applicant.
Currently marine gasoline fuel systems built for use in the United States are regulated by the Code of Federal Regulations, Title 33, as well as optional voluntary industry standards from the American Boating and Yacht Council, referred to as ABYC H-24.
Critical guidelines from these regulations pertain to the background art, including:
33 CFR §183.518                Each opening into the fuel tank must be at or above the topmost surface of the tank.        
33 CFR §183.520                (a) Each fuel tank must have a vent system that prevents pressure in the tank from exceeding 90 percent of the pressure marked on the tank under §183.514(b)(5).        (b) Each vent must:                    (1) Have a flame arrester that can be cleaned unless the vent is itself a flame arrestor; and            (2) Not allow a fuel overflow at the rate of up to two gallons per minute to enter the boat.                        
ABYC H-24                24.5.1 The installed fuel system shall be designed so that a fuel temperature rise of 60° F. (33° C.) shall not cause liquid fuel to spill into the boat or the environment when:                    24.5.1.1 the fuel tank is filled to its rated capacity according to the boat manufacturer's instructions, and            24.5.1.2 the boat is in the static floating position.                        NOTE: A fuel system designed to contain five percent fuel expansion is one method of meeting this requirement.        24.10.3 Tank connections, fittings and liquid level gauges and transmitters shall be readily accessible or accessible through an access panel, port or hatch.        
Manufacturers typically comply with ABYC H-24.5.1 by recommending in their instruction manuals that owners limit filling the fuel tank to 95% of its maximum rated capacity. In conventional designs there are limited known alternatives to creating a “ullage”, which is the amount by which the gasoline falls short of completely filling the fuel tank, and at the same time complying with CFR §183.518 cited above with respect to openings in the top most surface of the fuel tank.
The cited 5% ullage in the tank is required so that as fuel expands due to diurnal temperature changes, the fuel does not expand into the ventilation line, or alternatively the fuel cannot be expelled out of the fuel system and into the vessel or the environment.
A movement has begun in the marine industry to establish further standards and requirements which address diurnal fuel emissions, and will result in mandatory standards requiring boat manufactures to design and install diurnal emission controls on new vessels.
In conventional practice, there are currently two primary options used by manufactures to comply with the EPA diurnal emissions control regulations. The first involves the installation of a carbon filled canister within the ventilation line in order to trap hydrocarbons that are contained in the ventilated air. The ventilated air is expelled out of the ventilation line through the diurnal temperature changes which cause the gasoline to expand and contract. The second involves the installation of pressure relief valve system which encapsulates the fuel emissions by sealing the tank until the pressure exceeds a predetermined value, such as one psi.
There is nothing presently known in conventional practice or in the background art which takes into account the phenomenon described above, acts as a fuel system ullage float valve of precision design and operation, and functions at maximum efficiency in preventing undesired back flow or flow through the ventilation lines or any included valve or canister assemblies. Therefore, there exists a need for a fuel system ullage float valve assembly which accounts for diurnal temperature and pressure changes and fuel expansion, and prevents the deleterious effects described above.